Re: [PATCH net 1/2] macvlan: forbid L2 fowarding offload for macvtap

[David Miller <davem@davemloft.net>]

From: Jason Wang <jasowang@redhat.com>
Date: Tue, 07 Jan 2014 11:17:06 +0800

> On 01/07/2014 04:47 AM, David Miller wrote:
>> From: Jason Wang <jasowang@redhat.com>
>> Date: Mon,  6 Jan 2014 11:21:06 +0800
>>
>>> L2 fowarding offload will bypass the rx handler of real device. This will make
>>> the packet could not be forwarded to macvtap device. Another problem is the
>>> dev_hard_start_xmit() called for macvtap does not have any synchronization.
>>>
>>> Fix this by forbidding L2 forwarding for macvtap.
>>>
>>> Cc: John Fastabend <john.r.fastabend@intel.com>
>>> Cc: Neil Horman <nhorman@tuxdriver.com>
>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> I think I agree with Neil that the rx_handler change might be the best
>> way to fix this.  That change seems to have a lot of nice unintended
>> side effects, no?
> 
> Not all sides effects are nice.
> 
> One obvious issue is it disables the multiqueue macvtap transmission,
> since all queues will contend on a single qdisc lock of macvlan. And
> even more, multiqueue macvtap support creating and destroying a queue on
> demand which is not supported by L2 forwarding offload.
> 
> So L2 forwarding offload needs more fixes to let the multiqueue macvtap
> works. Currently, we really need this patch to make sure macvtap works
> as expected.

Ok I moved these two patches back to "Under Review".

These are pretty last minute and we'll need to make a decision on
what to do before Friday if you want these changes to really make
it into 3.13